For many years surgical wounds and other internal and skin wounds, have been closed using sutures and needles. In more recent times a number of skin stapling instruments have been developed. These instruments apply a series of metal staples to an external wound; that is, a skin wound, to close the wound. In many instances, such skin stapling instruments have replaced the suturing of such wounds. Also, in more recent times instruments have been developed to apply metal fasteners such as staples internally to close internal wounds during a surgical procedure. The primary advantages of the instruments which apply staples to wounds is that they greatly reduce the time required to close the wound and present minimum traumatic effects to improved healing of tissue. Both factors lead to reduced blood loss and improved patient care. Thus, these instruments have considerable medical benefits and economic benefits in surgical procedures. A major disadvantage of closing wounds with metallic staples is that very often the patient requires subsequent diagnostic procedures such as x-rays, CT scanning, and the like, and the metal staples often disrupt such diagnostic procedures. To overcome this last drawback, a number of polymeric fastening systems have been developed which use fasteners made from polymeric materials placed by a suitable instrument to close the wound. Examples of such fastening systems are more fully disclosed in U.S. Pat. Nos. 4,060,089, 4,532,927, 4,532,926 and 4,513,746.
In European patent application No. 84401937.2, Publication No. 0136949, there is disclosed a surgical fastening system made from polymeric materials which has a primary use of closing internal wounds. The system comprises a two-piece fastening member that is a staple which penetrates the tissue to be closed and a retainer or receiver which interlocks with that staple once it has penetrataed the tissue to maintain the wound closed. In this patent, the retainers are connected to one another by yieldable links, that is, flexible or frangible links. The links are used to maintain the receivers together to assist in loading instruments with the receivers, and it is desired that once applied to the tissue the links break so as not to restrict movement of the tissue.
When making polymeric fastening systems of either absorbable or non-absorbable polymers, the staple legs should penetrate the tissue with the least amount of trauma. Once the legs have penetrated the tissue, they should be reliably locked in place by the receiver. To lessen tissue trauma, it is desirable to reduce the insertion force required for the staple leg to penetrate tissue. The insertion force may be reduced by reducing the cross-sectional area of the staple leg. However, the smaller the cross-sectional area of a staple leg, the more it is apt to deform or misalign with the opening in the interlocking receiver.
What has now been discovered is a specific structure of a fastening system comprising staples and receivers wherein the insertion force to insert a staple leg through tissue is reduced and the misalignment of the staple leg and the receiver opening is also reduced while maintaining a reliable interlocking of the staple and receiver.